Pivoted-cylinders log turner means for handling logs



5 Sheets-Sheet 1 INVENTORS lllll |L G. E. BARGDILL ETAL (Il /mid 15 522 50271? [azure/me &' Fania/W000 BWJ ygbdiui I ATTORNEYSi PIVOTED-CYLINDERS LOG-TURNER MEANS FOR HANDLING LOGS Oct. 1, 1963 Filed Nov. 15, 1960 Oct. 1, 1963 e. E. BARGDILL ETAL 3,105,529

PIVOTED-CYLINDERS LOG-TURNER mus FOR HANDLING LOGS Filed Nov. 15, 1960 s Sheets-Sheet 2 INVENTORS 50 fie/mid 5 5475417! Lawrence 6. Fez/201M000 PIVOTED-CYLINDERS LOG-TURNER MEANS FOR HANDLING LOGS Filed Nov. 15, 1960 Oct. 1, 1963 (5.1:. BARGDlLl ETAL 3 Sheets-Sheet 5 5 R Z w Mm 2 n Be P 6 4 w WM 5 F w a ATTORNEYS position against the set works.

United States Patent 3,105,529 PIVOTED-CYLINDERS LOG TURNER MEANS FOR HANDLEJG LOGS Gerald E. Bargdill and Lawrence G. Penhorwood, both of Rte. 1, West Mansfield, Ohio Filed Nov. 15, 1960, Ser. No. 69,440 3 Claims. (Cl. 143-99) This invention relates generally to the handling of logs or timber, particularly for placing and arranging the same in position on the carriage for sawing.

In the operation of a saw mill logs are commonly moved from the location where a tree has been cut, onto a platform or deck from which they are then rolled successively onto a carriage and secured in position on the carriage to be moved by the carriage to the saw where the log is cut lengthwise into a number of sections or planks.

The logs are never completely circular, or only in rare instances are they completely circular, but they are frequently distorted or have large projecting parts or they have the stumps of branches projecting therefrom and these conditions of non-circular form or of having branch stumps projecting from the body of the log, cause difficulty in rolling the log onto the carriage and into When, by reason of a stump or a limb or for any other reason, the log will not roll properly into position on the carriage, it becomes necessary for one or more of the loggers or sawyers to manually shift and turn the log into the desired position on the head blocks which form a part of the carriage structure, by employment of cant books or peavys.

The turning and adjusting of the logs either on the log deck or on the head blocks on the carriage is a laborious and time-consuming operation.

-It is a particular object of the present invention, in the light of the foregoing, to provide a new and novel mechanism by means of which an operator can effect the automatic power lifting and turning of a log in such a way as to place it in a more desirable position either on the log deck or on the carriage head blocks so that it can be easily shifted into place to be secured by means of the conventional securing or toothed dog forming a part of the head blocks.

A further object of the invention .is to provide power mechanism for shifting and turning logs in the manner described, which is additionally designed so as to facilitate adjusting and/or arranging the position of a number of cants into which the log has been cut, for the purpose of further cutting the cants into timber of desired cross sectional form such as boards of selected width or beams, such as two-by-fours, two-by-eights, etc.

More particularly it is an object of the invention to provide a power operated mechanism by means of which the described operations can be performed easily and quickly, which mechanism is of relatively simple design or construction, as a result of which it can be economically built while at the same time the design or construction of the mechanism is such that it can be made of great strength and'dura-bility, as is necessary for the lifting and moving of logs of great weight and will, therefore, have a long serviceable life.

A still further object of the invention is to provide a power mechanism for lifting and turning logs in the manner stated, which mechanism includes in its structure a cant hook carried in a novel manner for actuation by the lifting mechanism whereby a log or timber may be pulled back from the carriage into a position where it can be conveniently turned over to be set in a new position for further cutting operation thereon.

The various advantages and objects of the present invention are attained through the provision of a pair of coupled fluid actuated power or lifting units controlled by manually manipulatable valves by which to direct operating fluid under pressure to the units and by means of which valves the two units may be made to perform simultaneously to accomplish a number of different log moving or timber moving actions. More particularly, the power units comprise two fluid operated pistons each of which actuates a piston rod and the outer end of one piston rod carries a pointed head or claw while the rod operatively coupled with the other piston is pivotally connected at its outer end to the first unit, either to the piston cylinder, or to the claw head, and the piston cylinders forming parts of the units are pivotally mounted for simultaneous swinging motion on spaced parallel axes. The control valves by which fluid under pressure is directed into and withdrawn from the inner and outer ends of the piston cylinders, are adapted to be manually manipulated simultaneously to eflfect a number of different movements of the cylinders and the pistons and piston rods to perform the desired variety of log and timber lifting and shifting movements.

.There is also provided a cant hook for pivotal attachment to the claw head carried by the one piston rod, by means of which desired pulling operations upon logs may be carried out to further assist in properly setting the logs on the carriage head blocks.

The invention will be best understood from a consideration of the following detail description taken in connection with the accompanying drawings forming part of the specification, with the understanding, however, that the invention is not confined to a strict conformity with the showing of the drawings but may be changed or modified so long as such changes or modifications mark no material departure from the salient features of the invention as expressed in the appended claims.

In the drawings:

FIG. 1 is a view illustrating diagrammatically and in top plan a deck structure and log carriage and showing the apparatus of the present invention mounted in operative position beneath the top of the log deck and adjacent to the carriage, the coupled cylinders of the apparatus being inclined forwardly in a position for en gagement of the claw head with the underside of a log;

FIG. 2 is an end elevational view of the log carriage and log deck and illustrating in full lines one operative position for the log shifting mechanism and showing in broken lines the apparatus in retracted position;

FIG. 3 (Sheet 1) is a vertical section taken substantially on the line 33 of FIG. 2;

FIG. 4 (Sheet 3) is a diagrammatic view of the fluid circuit by which the actuation of the pistons is effected;

FIG. 5 is a detail sectional view of one form of dual control valve for distributing fluid under pressure to the piston cylinders of the apparatus;

FIG. 6 (Sheet 1) is a diagrammatic view illustrating different steps in the movements of the coupled power units in the operation of raising a log from the carriage and replacing the same on the log deck to overcome the obstructing action of a limb, stump or other irregularity, to the placement of the log in position on the carriage for securement to the head blocks;

FIG. 7 illustrates diagrammatically the action of the mechanism for turning a number of cants and repositioning the same on the log carriage;

FIG. 8 is a detail view looking toward the back of the log engaging claw and showing the connection of the stabilizing rod therewith;

FIG. 9 illustrates the attachment to the log engaging claw by a pivot pin, of a cant hook, showing the hook and the claw in side elevation;

FIG. 10 is a view looking down on the top of the claw and the cant hook;

FIG. 11 is a diagrammatic view illustrating the use of the cant hook for turning a log on the log carriage;

FIG. 12 is a view illustrating another manner in which the primary and secondary power units may be coupled together for cooperative action.

Referring now more particularly to the drawings, the numeral generally designates a deck or platform structure designed to have placed upon the top thereof logs to be moved onto the log carriage. This log carriage is here generally designated 12 and, like the log deck, is diagrammatically illustrated and is shown in top plan in FIG. 1 while in FIG. 2 the deck and the carriage with the supporting under-parts are shown in elevation.

The log deck is here shown as comprising a number of top beams 14 arranged in spaced pmallelrelation and lying perpendicular to the long carriage structure upon which the log is placed to be sawed and the supporting beams 14 are in turn supported by an underlying structure which elevates the top of the deck above the ground. Such underlying structure for the log deck or the beams 14 making up the same, is here shown as embodying base beams 16 and vertically positioned posts 18, the

lower ends being connected with the base beams 16 and the upper ends being secured to and supporting the horizontal beams 14, with suitable intermediate strengthening rails 21 encircling the deck supporting framework.

The log deck structure is positioned, in the usual manner, at one side of the log carriage supporting structure 22. This structure is also conventionally illustrated and may comprise a number of upright posts 24 which support upon their upper ends suitable cross beams 26 and these beams in turn support the spaced parallel track rails 28 upon which run the carriage supporting wheels 30.

The body or floor of the carriage is designated 31 and this supports the usual head blocks 32 and upstanding knees 33 which in turn carry the log securing dogs 34. All of these units are diagrammatically illustrated merely to show the relation of the log turning apparatus with the other elements of the saw mill structure and do not, of course, constitute any part of the present invention aside from the association therewith of the log turning mechanism.

In accordance with the present invention there is provided a frame structure which is generally designated 34 and within which the hereinafter described power units are mounted. This frame structure is set approximately in the central portion of the log deck and opens upwardly and forwardly through the top of the deck and toward the carriage supporting structure 22; The frame structure 34 preferably comprises a heavy base plate 36 upon which are set in upright position, or on edge, the two spaced parallel heavy side wall plates 38 and these plates are reinforced around their edges and on the outer or remote sides thereof by angle bars or angle beams 39 which border the top, front and back edges of the plates. To further rigidity the frame structure the rear thereof, being the side remote from the carriage supporting structure 22, may be closed by the heavy vertical back plate 40 which may extend to the top edges of the side plates 38 and the front of the frame structure 34 may be closed partway up from the base plate 36 by the low or half-wall 41. The height of this latter wall is such as not to interfere with the forward swinging movement of one of the power units nearest thereto.

Enclosed within the frame structure 34 are two cooperatively joined or coupled power units which are spaced apart in a plane lying perpendicular to the back and front walls 40 and 41, or, in other words, parallel with and midway between the side wall plates 38. The forwardmost one of these power units is generally designated 42 and constitutes the main unit of the apparatus, while the rearmost unit is generally designated 43 and constitutes the auxiliary unit which functions in cooperation with the main unit.

secured at its ends in the plates 38, as shown in FIG. 3.

The cylinder 44 has a piston 51 therein which is connected with the piston rod 52 and the upper end of this piston rod 52 carries a claw 53. This claw 53 comprises the two arcuate members 54 disposed in spaced relation and having the upper end of the piston rod connected therewith, in a line passing midway therebetween, and at approximately midway between the ends of the members. The connection of the piston rod 52 with the members 54 may be made in any suitable manner as, for example, by means of the heavy boss 54' which joins the members 54 and may extend downwardly below the same as illus trated in PEG. 8 and this boss may be socketed to receive the upper end of the piston rod 52 and the two parts may be welded together or any other suitable means may be employed for solidly coupling the rod 52 with the claw head which will ensure a strong construction and one which will not fail under the strain of lifting a log or under any twisting strain which may be imposed thereon. Each of the members 54 is of substantial construction and the members of the claw are disposed with the concave sides thereof uppermost and each member further terminates in an upwardly extending point 55 (FIGS. 9 and 10) while the opposite end of each member extends rearwardly beyond the adjacent piston rod 52 and the heavy rear ends 56 of the two members 54 of the claw are apertured at 57 to receive a suitable cross pin or bolt for the purpose about to be described.

Forwardly of the piston rod 52 or toward the pointed ends 55, the members 54 are apertured to receive a heavy cross pin or bolt 58 by means of which a cant hook may be pivotally coupled to the claw as illustrated in FIGS. 9 and 10. Such cant hook is generally designated 5.

The cant hook 59 is connected to the claw 53 for the carrying out of certain operations where it is necessary to pull a log or a num er of pieces of material from the carriage toward the platform, particularly where the log 7 is to be turned over to another position for making a second cut, as hereinafter described.

a The cant hook 5% comprises the long slightly arcuate body portion 6%) which terminates at one end and on the concave side of the body 69, in the sharply pointed reversely curving hook 61. The opposite end of the cant hook body 69 is bifurcated as shown in FIG. 10, the two furcations 62 being designated to straddle the two members 54 of the claw 53 and the furcations are suitably apertured to have the coupling pin 53 passed therethrough whereby the cant hook can swing on the claw toward and away from the pointed ends of the members 54. Also as will be readily apparent, the body on of the cant hook is of substantial length so that when it is swung forwardly it will extend a substantial distance beyond the pointed ends of the members 54 of the claw.

In order that the claw head 53 of the piston rod 52 may be maintained in proper working position or held against rotation on the axis of the piston and piston rod, a restraining or stabilizing guide means is provided in the form of a relatively long tube or sleeve 63, see FIGS.

1 and 3, which is secured longitudinally of and to the cylinder 44 and has slidable therein the rod 64 the top end of which is firmly secured as at 65 in a boss 66 integral with or forming a part of the adjacent side of the claw head 53. Thus as the piston rod moves back and forth with the claw head 53 in engagement with a log or other piece of timber, the head and piston rod will be held against turning and the head will not slip out o engagement with the timber.

The auxiliary or secondary power unit which is generally designated 43 also comprises a piston cylinder 67 in which is slidably housed a piston, not shown, having conected with it the piston rod 68 which extends from the upper end of the cylinder as illustrated. The auxiliary unit piston rod 68 in the preferred embodiment of the invention is secured to the upper portion of the primary unit whereby upon extension of the auxiliary piston rod, or upon its retraction, the primary unit will be oscillated as desired.

The preferred manner of coupling the upper end of the auxiliary piston rod 68 with the primary unit is by means of a collar or band 44a (FIG. 11) secured around the cylinder 44 adjacent to the top end thereof and which band has its ends extended rearwardly to form the spaced ears 44b which are apertured to receive a suitable bolt which is extended through the apertured upper end of the piston rod 63 when the latter is located between the ears.

The bottom end of the auxiliary power unit cylinder 67 is mounted upon a rocking support, see FIG. 1, which is generally designated 69 and which, like the support 45 for the main power unit cylinder, is here shown as of inverted substantially U-shape having the mid portion 70 terminating in the downturned ends or legs 71 which are supported by a transverse shaft 72 which extends through the legs and has its ends fixed in the frame plates 33.

The pivot shaft 72 is disposed in the frame structure 34 rearwardly of the shaft 54) which supports the forward cylinder 44. These pivot shafts 50 and 72 are in parallel relation so that the two power units may swing as one when desired and in the operation of extending or retracting the pistons and piston rods thereof.

As hereinbefore stated, the power units are operated by fluid pressure, preferably hydraulic pressure, and FIGS. 4 and 5 illustrate respectively the fluid circuit lay-out for the fluid system, in which the cylinders 44 and 67 are elements, and the details of the dual manual control valve structure by means of which the pistons of the cylinders are extended or moved outwardly and inwardly as desired.

The control valve structure is generally designated 73 and in the circuit diagram the numerals 74 and 75 respectively designate the hydraulic fluid supply tank and the pump for delivering the fluid from the tank through the valve structure to the selected cylinders.

While any dual manual control valve suitable for selectively delivering fluid under pressure to the piston cylinders 44 and 67 from the source and returning the same thereto, may be employed, there is here illustrated one type of valve by which the desired operation may be accomplished.

The valve here shown is of the type illustrated and described in Patent 2,684,696, and since it in the details thereof forms no part of the present invention but is merely shown to illustrate one means by which the fluid flow may be controlled, only a suflicient description of its structure will be set forth to understand the flow of fluid into and out of the cylinders.

In the illustrated valve structure of FIG. 5, the numeral 76 designates an inlet port which is connected with the supply line 77 leading from the pump 75 While the numeral 78 designates the outlet port of the valve which is connected by the fluid line 79 with the return to the fluid tank 74.

The valve structure has the four fluid ports 80, 81, 82 and 83 and the dual control manuals 84 and 85. These manuals 84 and 85 are operable one independently of the other and by their means the fluid flow can be controlled in the manner about to be described.

As will be seen upon reference to FIG. 4, one manual, here designated 84, controls the flow of fluid under pressure from the source to the secondary power unit cylinder 67 while the other manual 85 controls the flow of fluid under pressure to and from the primary power unit cylinder 44. By shifting the manual in the desired direction, fluid may be introduced into the cylinder 44 by way of the port 82 and conduit 86- which is connected with the lower end of the cylinder 44 at the nipple 87 so as to effect the outward movement of the piston rod 52 and fluid in the cylinder will be returned from the nipple 88 to and through the conduit 89 to the port 83. Reverse movement of the manual 85 will permit the fluid under pressure to flow in the reverse direction whereby to enter the upper end of the cylinder 44 and leave by the lower end so as to retract the piston 52.

Likewise for the manipulation of the piston in the cylinder 67 appropriate movement of the manual 84 will permit fluid to flow through the valve from the source by way of the port 80 to the conduit 89 which is connected with a suitable nipple or coupling 90 leading into the lower end of the cylinder Whereb-y to move the piston rod 68 outwardly and fluid in the cylinder above the outwardly moving piston will be returned through the port 91 to the conduit 92 which leads back to the valve port 81 from Where it will flow to the supply reservoir 74. By thus controlling the fluid flow by the dual manual valve unit, it will be seen that the two power units which are coupled together for unitary operation can be given a variety of movements for shifting and turning logs or beams on the saw carriage or on the log deck through the medium of the claw head 53 functioning alone as illustrated diagrammatically in FIG. 6 or in FIG. 7, or by the combined use of the claw head and the attached cant hook 59 in the manner illustrated in FIG. 11.

For illustrating one Way of using the coupled power units reference is directed to FIG. 6 which shows diagrammatically how a log which has been rolled onto the log carriage and which cannot be turned conveniently into position against the head block, may be raised and brought back to a position on the log deck where it may then be rolled over or turned by the apparatus without difliculty. In this view the log is generally designated 93 and, as shown, a limb stump or other enlargement 94 thereon is engaging the surface of the carriage so that it cannot be conveniently rolled over to position against the head block 33.

By then extending the piston rod 52 of the principal power unit 42 so as to bring the claw head 53 into position against the underside of the log as shown in this diagrammatic view and also in FIG. 2, the portion of the log lying with the stump 94 upon the carriage can be elevated from the carriage and after being so elevated by the extension of the piston 52, by introducing the fluid into the top end of the secondary or auxiliary cylinder 67, a rearward pull can be applied to the top end of cylinder 44 so as to swing the primary cylinder back away from the log carriage in approximately the position indicated in FIG. 6 by the reference character a and then lowered onto the log deck to the approximate position indicated at b in FIG. 6. As will be readily apparent, a turning or rolling action will be imparted to the log by reason of its being moved reversely through an are so that it will roll over and come to rest upon the log deck with the stump or irregular side projection 94 thereof raised from the deck.

The two power units may then be swung back to a fully retracted position. The principal power unit can then be employed to lift the log and move it forward and replace it on the log carriage in a position where the portion 94 thereof will not interfere with its being rolled sufliciently to bring it to rest upon the head block and against the knees 33. This action will, of course, be carried out by engaging the underside of the log with the claw head and lifting the log and then shifting it back onto the carriage, as will be readily understood.

In the operation of sawing a log into a number of planks or cants, it may be desired to turn the several cants from the on-edge position, as illustrated in FIG. 7, to a position in which they lie on their sides so that they can be out again to form a number of timbers of small size, such as 2 x 4, 2 x 8 or the like. In FIG. 7 the numeral 95 generally designates a number of cants each of which is designated 96 and as shown in full lines, these cants are positioned on edge on the log carriage. The claw head is shown in the full line position it would assume when used to push the cants back against the head block.

To turn the cants on their sides, the claw head would be moved to approximately the position in which it is shown in broken outline, in FIG. 7. Then by using a conventional manual cant hook, or by using the cant hook 60 attached to the claw head, the cants may be turned over and let down to the position in which they are shown in broken lines, onto the point of the claw head. The claw head is then moved forward and lowered to lower the cants onto their sides. After the lowermost cant is lying on its side on the carriage, any straightening which may be required to bring the cants back into edge-alignment can be effected by pushing with the forward side of the head against the outer edges of the cants.

FIG. 11 shows one manner of using the cant hook 59 when it is pivotally coupled with the claw head 53, for the purpose of turning a log to a new position on the carriage. Heretofore manually employed cant hooks have been used for this purpose, but with the present invention it is only necessary to raise the claw head 53 to the desired elevation and swing the cant hook over to efiect engagement of the point thereof with the log whereupon the simultaneous operation of the two power units can be eifected to pull the cant hook over in the proper direction to turn the log and after it has been turned to its new position, then the forward side of the claw head may be placed against the log and by extending the piston rod 63 of the secondary power unit, the log can be shoved back into position against the head block.

While the structure thus far described has been directed to the arrangement where the outer end of the secondary power unit piston rod 68 is pivotally attached to the cylinder 44 of the main unit 42, this piston rod may also be coupled to the back end of the claw head as illustrated in FIG. 12.

In this latter figure the principal power unit cylinder is designated 44 and the auxiliary power unit cylinder is designated 69'.

The piston rod 52 of the primary cylinder 44 carries the claw head as in the previously described structure, which claw head here is generally designated 53.

To efiect the connection of the upper end of the piston rod '68 with the rear of the claw head, the rod 68' is suitably formed to position between the rear ends of the claw head portions and it is apertured to receive the bolt 57a which is extended through the apertures 57 in the claw head portions and through the aperture of the piston rod 68.

It will be readilyseen that by the arrangement shown in FIG. 12 the secondary power unit can function in a manner similar to the structure previously described to force the primary unit cylinder to swing back and forth as may be desired, simultaneously with the extension and retraction of the primary unit piston rod 52. In this manner of coupling together the two power units it will be seen that the extension of the secondary unit piston rod will assist the outward movement of the claw head carried by piston rod 52. Otherwise the cooperative relation and cooperative action of the two units is the same.

From the foregoing it will be apparent that there is provided by the present invention a relatively simple log handling or log moving and positioning mechanism by means of which a number of different movements may be imparted to a log, either in its initial form as placed upon the log deck and carriage, or after it has been partially sawed or after it has been cut into a number of cants in the manner illustrated in FIG. 7. Furthermore it will be seen that the mechanism is such that it can be constructed in sufficient size and of proper strength to handle logs of very large size and also to have long life under the severe treatment or usage to which mechanism of this character is subjected.

We claim: 1. Saw mill apparatus for moving logs forwardly from a log deck onto a carriage and vice versa; said apparatus comprising a log deck structure having a forward side to position adjacent to a log carriage and a substantially horizontal open top for supporting logs substantially parallel to said forward side, an elongate upstanding forward power unit embodying a fluid cylinder, piston and piston rod, a pivotal support below said deck top having said cylinder mounted at its lower end thereon for forward and back rocking movement in a substantially vertical plane and between a forwardly inclined position in which the top end of the piston rod extends forwardly beyond the forward side of the deck, to a rearwardly inclined retracted position, an auxiliary power unit embodying a fluid cylinder, piston and piston rod, a pivotal support rearwardly of the first support having the auxiliary unit cylinder mounted thereon rearwardly of the first unit cylinder for swinging movement in said plane, a pivot coupling between the upper end of the auxiliary unit piston rod and an upper part of the forward power unit, fluid conducting conduits connected to the top and bottom ends of each unit cylinder, valve means connected with said conduits and operable to selectively direct fluid under pressure from a source into either end of each cylinder while exhausting fluid from the other end of the cylinder and thereby effect selective in and out movement of the piston rods of said units, a relatively long arcuate log engaging claw rigidly secured substantially midway between its ends and on the convex side thereof to the top end of the forward power unit piston rod, said claw having one end terminating in a point which is directed forwardly and upwardly and the said concave side of the claw beingdirected upwardly to engage across a rounded underside of a log, said'forward power unit when in its said retracted position being operable to position the claw at an elevation below the deck top.

2. The invention according to claim 1, with an elongate extensible guide means at one side of and parallel with the cylinder of said forward unit and operatively coupled with and between the said cylinder and piston rod of that unit, to hold the latter position rod against axial turning while it is being moved longitudinally.

3. The invention according to claim 1, with an elongate cant hook having a pointed end and an opposite bi furcated end, said bifurcated end being dimensioned to straddle, and being in straddling relation with, the claw forwardly of the point of connection or" the claw with the supporting piston rod, a pivot pin extending transversely through said bifurcated end and through the claw, and said cant hook having a rearwardly swung position in which it rests, adjacent the said bifurcated end thereof, upon the upwardly directed concave side of the claw.

References Cited in the file of this patent UNITED STATES PATENTS 139,578 Hinkley et 'al. June 3, 1873 466,682 Hill Jan. 5, 1892 559,192 McNerney Apr. 28, 1896 569,366 Wilkin Oct. 13, 1896 1,047,599 Whittaker Dec. 17, 1912 2,484,362 Weber Oct. 11, 1949 2,571,177 Allen 'Oct. 16, 1951 2,655,185 Richardson Oct. 13, 1953 2,684,696 Gurries et a1. July 27, 1954 2,765,006 Maynard Oct. 2, 1956 

1. SAW MILL APPARATUS FOR MOVING LOGS FORWARDLY FROM A LOG DECK ONTO A CARRIAGE AND VICE VERSA; SAID APPARATUS COMPRISING A LOG DECK STRUCTURE HAVING A FORWARD SIDE TO POSITION ADJACENT TO A LOG CARRIAGE AND A SUBSTANTIALLY HORIZONTAL OPEN TOP FOR SUPPORTING LOGS SUBSTANTIALLY PARALLEL TO SAID FORWARD SIDE, AN ELONGATE UPSTANDING FORWARD POWER UNIT EMBODYING A FLUID CYLINDER, PISTON AND PISTON ROD, A PIVOTAL SUPPORT BELOW SAID DECK TOP HAVING SAID CYLINDER MOUNTED AT ITS LOWER END THEREON FOR FORWARD AND BACK ROCKING MOVEMENT IN A SUBSTANTIALLY VERTICAL PLANE AND BETWEEN A FORWARDLY INCLINED POSITION IN WHICH THE TOP END OF THE PISTON ROD EXTENDS FORWARDLY BEYOND THE FORWARD SIDE OF THE DECK, TO A REARWARDLY INCLINED RETRACTED POSITION, AN AUXILIARY POWER UNIT EMBODYING A FLUID CYLINDER, PISTON ND PISTON ROD, A PIVOTAL SUPPORT REARWARDLY OF THE FIRST SUPPORT HAVING THE AUXILIARY UNIT CYLINDER MOUNTED THEREON REARWARDLY OF THE FIRST UNIT CYLINDER FOR SWINGING MOVEMENT IN SAID PLANE, A PIVOT COUPLING BETWEEN THE UPPER END OF THE AUXILIARY UNIT PISTON ROD AND AN UPPER PART OF THE FORWARD POWER UNIT, FLUID CONDUCTING CONDUITS CONNECTED TO THE TOP AND BOTTOM ENDS OF EACH UNIT CYLINDER, VALVE MEANS CONNECTED WITH 